note
	description: "Intervals between absolute values"
	legal: "See notice at end of class."
	status: "See notice at end of class."
	date: "$Date: 2018-12-18 10:46:58 +0000 (Tue, 18 Dec 2018) $"
	revision: "$Revision: 102623 $"

class 
	INTERVAL [G -> ABSOLUTE]

create 
	make

feature -- Initialization

	make (s, e: G)
			-- Sets start_bound and end_bound to s and e respectively.
		require
			start_exists: s /= Void
			end_exists: e /= Void
			start_before_end: s <= e
		do
			start_bound := s
			start_bound := start_bound.deep_twin
			end_bound := e
			end_bound := end_bound.deep_twin
		ensure
			start_bound_set: start_bound /= Void and then deep_equal (start_bound, s)
			end_bound_set: end_bound /= Void and then deep_equal (end_bound, e)
		end
	
feature {NONE} -- Initialization

	default_create
			-- Process instances of classes with no creation clause.
			-- (Default: do nothing.)
			-- (from ANY)
		do
		end
	
feature -- Access

	end_bound: G
			-- End bound of the current interval.

	generating_type: TYPE [detachable INTERVAL [G]]
			-- Type of current object
			-- (type of which it is a direct instance)
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			generating_type_not_void: Result /= Void
		end

	generator: STRING_8
			-- Name of current object's generating class
			-- (base class of the type of which it is a direct instance)
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			generator_not_void: Result /= Void
			generator_not_empty: not Result.is_empty
		end

	start_bound: G
			-- Start bound of the current interval.
	
feature -- Measurement

	duration: DURATION
			-- Length of the interval.
		do
			Result := end_bound.duration - start_bound.duration
		end
	
feature -- Comparison

	frozen deep_equal (a: detachable ANY; b: like arg #1): BOOLEAN
			-- Are a and b either both void
			-- or attached to isomorphic object structures?
			-- (from ANY)
		do
			if a = Void then
				Result := b = Void
			else
				Result := b /= Void and then a.is_deep_equal (b)
			end
		ensure -- from ANY
			instance_free: class
			shallow_implies_deep: standard_equal (a, b) implies Result
			both_or_none_void: (a = Void) implies (Result = (b = Void))
			same_type: (Result and (a /= Void)) implies (b /= Void and then a.same_type (b))
			symmetric: Result implies deep_equal (b, a)
		end

	frozen equal (a: detachable ANY; b: like arg #1): BOOLEAN
			-- Are a and b either both void or attached
			-- to objects considered equal?
			-- (from ANY)
		do
			if a = Void then
				Result := b = Void
			else
				Result := b /= Void and then a.is_equal (b)
			end
		ensure -- from ANY
			instance_free: class
			definition: Result = (a = Void and b = Void) or else ((a /= Void and b /= Void) and then a.is_equal (b))
		end

	includes (other: like Current): BOOLEAN
			-- Does current interval include other?
		do
			Result := other.is_included_by (Current)
		end

	intersects (other: like Current): BOOLEAN
			-- Does current interval intersect other?
		require
			other_exists: other /= Void
		do
			Result := start_bound.max (other.start_bound) <= end_bound.min (other.end_bound)
		end

	frozen is_deep_equal (other: INTERVAL [G]): BOOLEAN
			-- Are Current and other attached to isomorphic object structures?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		external
			"built_in"
		ensure -- from ANY
			shallow_implies_deep: standard_is_equal (other) implies Result
			same_type: Result implies same_type (other)
			symmetric: Result implies other.is_deep_equal (Current)
		end

	is_equal (other: like Current): BOOLEAN
			-- Is current interval equal to other?
		require -- from ANY
			other_not_void: other /= Void
		do
			Result := start_bound.is_equal (other.start_bound) and then end_bound.is_equal (other.end_bound)
		ensure -- from ANY
			symmetric: Result implies other ~ Current
			consistent: standard_is_equal (other) implies Result
		end

	is_greater alias ">" (other: like Current): BOOLEAN
			-- Is current interval after other?
		do
			Result := other < Current
		end

	is_greater_equal alias ">=" (other: like Current): BOOLEAN
			-- Is current interval after other?
		do
			Result := other <= Current
		end

	is_included_by (other: like Current): BOOLEAN
			-- Is current interval included by other?
		do
			Result := start_bound >= other.start_bound and then end_bound <= other.end_bound
		end

	is_less alias "<" (other: like Current): BOOLEAN
			-- Is current interval strictly before other?
		do
			Result := start_bound < other.start_bound and then end_bound < other.end_bound
		end

	is_less_equal alias "<=" (other: like Current): BOOLEAN
			-- Is current interval before other?
		do
			Result := Current < other or else is_equal (other)
		end

	is_met_by (other: like Current): BOOLEAN
			-- Is current interval met by other?
		require
			other_exists: other /= Void
		do
			Result := other.meets (Current)
		ensure
			symmetry: Result = other.meets (Current)
		end

	is_overlapped_by (other: like Current): BOOLEAN
			-- Is current interval overlapped by other?
		require
			other_exists: other /= Void
		do
			Result := other.overlaps (Current)
		ensure
			symmetry: Result = other.overlaps (Current)
		end

	is_strict_included_by (other: like Current): BOOLEAN
			-- Is current interval strictly included by other?
		do
			Result := start_bound > other.start_bound and then end_bound < other.end_bound
		end

	meets (other: like Current): BOOLEAN
			-- Does current interval meet other?
		require
			other_exists: other /= Void
		do
			Result := end_bound.is_equal (other.start_bound)
		ensure
			symmetry: Result = other.is_met_by (Current)
			result_definition: Result = (Current <= other and intersects (other))
		end

	overlaps (other: like Current): BOOLEAN
			-- Does current interval overlap other?
		require
			other_exists: other /= Void
		do
			Result := end_bound >= other.start_bound and then start_bound <= other.start_bound and then end_bound < other.end_bound
		ensure
			result_defition: Result = (strict_before (other.end_bound) and has (other.start_bound))
			symmetry: Result = other.is_overlapped_by (Current)
		end

	frozen standard_equal (a: detachable ANY; b: like arg #1): BOOLEAN
			-- Are a and b either both void or attached to
			-- field-by-field identical objects of the same type?
			-- Always uses default object comparison criterion.
			-- (from ANY)
		do
			if a = Void then
				Result := b = Void
			else
				Result := b /= Void and then a.standard_is_equal (b)
			end
		ensure -- from ANY
			instance_free: class
			definition: Result = (a = Void and b = Void) or else ((a /= Void and b /= Void) and then a.standard_is_equal (b))
		end

	frozen standard_is_equal (other: INTERVAL [G]): BOOLEAN
			-- Is other attached to an object of the same type
			-- as current object, and field-by-field identical to it?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		external
			"built_in"
		ensure -- from ANY
			same_type: Result implies same_type (other)
			symmetric: Result implies other.standard_is_equal (Current)
		end

	strict_includes (other: like Current): BOOLEAN
			-- Does current interval strictly include other?
		do
			Result := other.is_strict_included_by (Current)
		end
	
feature -- Status report

	after (v: G): BOOLEAN
			-- Is the current interval after v?
		require
			exists: v /= Void
		do
			Result := start_bound >= v
		ensure
			result_definition: Result = (start_bound >= v)
		end

	before (v: G): BOOLEAN
			-- Is the current interval before v?
		require
			exists: v /= Void
		do
			Result := end_bound <= v
		ensure
			result_definition: Result = (end_bound <= v)
		end

	conforms_to (other: ANY): BOOLEAN
			-- Does type of current object conform to type
			-- of other (as per Eiffel: The Language, chapter 13)?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		external
			"built_in"
		end

	empty: BOOLEAN
			-- Is current interval empty?
		do
			Result := start_bound.is_equal (end_bound)
		ensure
			result_definition: Result = duration.is_equal (duration.zero)
		end

	has (v: G): BOOLEAN
			-- Does current interval have v between its bounds?
		require
			exists: v /= Void
		do
			Result := start_bound <= v and then end_bound >= v
		ensure
			result_definition: Result xor not (start_bound <= v and then end_bound >= v)
		end

	same_type (other: ANY): BOOLEAN
			-- Is type of current object identical to type of other?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		external
			"built_in"
		ensure -- from ANY
			definition: Result = (conforms_to (other) and other.conforms_to (Current))
		end

	strict_after (v: G): BOOLEAN
			-- Is the current interval strictly after v?
		require
			exists: v /= Void
		do
			Result := start_bound > v
		ensure
			result_definition: Result = (start_bound > v)
		end

	strict_before (v: G): BOOLEAN
			-- Is the current interval strictly before v?
		require
			exists: v /= Void
		do
			Result := end_bound < v
		ensure
			result_definition: Result = (end_bound < v)
		end
	
feature -- Element change

	set_end_bound (e: G)
			-- Set end_bound to e.
		require
			end_bound_exists: e /= Void
			end_after_start_bound: e >= start_bound
		do
			end_bound := e
			end_bound := end_bound.deep_twin
		ensure
			end_bound_set: equal (end_bound, e)
		end

	set_start_bound (s: G)
			-- Set start_bound to s.
		require
			start_bound_exists: s /= Void
			start_before_end_bound: s <= end_bound
		do
			start_bound := s
			start_bound := start_bound.deep_twin
		ensure
			start_bound_set: equal (start_bound, s)
		end
	
feature -- Duplication

	frozen clone (other: detachable ANY): like other
		obsolete "Use `twin' instead. [2017-05-31]"
			-- Void if other is void; otherwise new object
			-- equal to other
			--
			-- For non-void other, clone calls copy;
			-- to change copying/cloning semantics, redefine copy.
			-- (from ANY)
		do
			if other /= Void then
				Result := other.twin
			end
		ensure -- from ANY
			instance_free: class
			equal: Result ~ other
		end

	copy (other: INTERVAL [G])
			-- Update current object using fields of object attached
			-- to other, so as to yield equal objects.
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
			type_identity: same_type (other)
		external
			"built_in"
		ensure -- from ANY
			is_equal: Current ~ other
		end

	frozen deep_clone (other: detachable ANY): like other
		obsolete "Use `deep_twin' instead. [2017-05-31]"
			-- Void if other is void: otherwise, new object structure
			-- recursively duplicated from the one attached to other
			-- (from ANY)
		do
			if other /= Void then
				Result := other.deep_twin
			end
		ensure -- from ANY
			instance_free: class
			deep_equal: deep_equal (other, Result)
		end

	frozen deep_copy (other: INTERVAL [G])
			-- Effect equivalent to that of:
			--		copy (other . deep_twin)
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		do
			copy (other.deep_twin)
		ensure -- from ANY
			deep_equal: deep_equal (Current, other)
		end

	frozen deep_twin: INTERVAL [G]
			-- New object structure recursively duplicated from Current.
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			deep_twin_not_void: Result /= Void
			deep_equal: deep_equal (Current, Result)
		end

	frozen standard_clone (other: detachable ANY): like other
		obsolete "Use `standard_twin' instead. [2017-05-31]"
			-- Void if other is void; otherwise new object
			-- field-by-field identical to other.
			-- Always uses default copying semantics.
			-- (from ANY)
		do
			if other /= Void then
				Result := other.standard_twin
			end
		ensure -- from ANY
			instance_free: class
			equal: standard_equal (Result, other)
		end

	frozen standard_copy (other: INTERVAL [G])
			-- Copy every field of other onto corresponding field
			-- of current object.
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
			type_identity: same_type (other)
		external
			"built_in"
		ensure -- from ANY
			is_standard_equal: standard_is_equal (other)
		end

	frozen standard_twin: INTERVAL [G]
			-- New object field-by-field identical to other.
			-- Always uses default copying semantics.
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			standard_twin_not_void: Result /= Void
			equal: standard_equal (Result, Current)
		end

	frozen twin: INTERVAL [G]
			-- New object equal to Current
			-- twin calls copy; to change copying/twinning semantics, redefine copy.
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			twin_not_void: Result /= Void
			is_equal: Result ~ Current
		end
	
feature -- Basic operations

	frozen as_attached: attached INTERVAL [G]
		obsolete "Remove calls to this feature. [2017-05-31]"
			-- Attached version of Current.
			-- (Can be used during transitional period to convert
			-- non-void-safe classes to void-safe ones.)
			-- (from ANY)
		do
			Result := Current
		end

	frozen default: detachable INTERVAL [G]
			-- Default value of object's type
			-- (from ANY)
		do
		end

	frozen default_pointer: POINTER
			-- Default value of type POINTER
			-- (Avoid the need to write p.default for
			-- some p of type POINTER.)
			-- (from ANY)
		do
		ensure -- from ANY
			instance_free: class
		end

	default_rescue
			-- Process exception for routines with no Rescue clause.
			-- (Default: do nothing.)
			-- (from ANY)
		do
		end

	frozen do_nothing
			-- Execute a null action.
			-- (from ANY)
		do
		ensure -- from ANY
			instance_free: class
		end

	gather (other: like Current): like Current
			-- Union of other and current interval if other meets
			-- current interval.
		require
			other_exist: other /= Void
			meeting_interval: meets (other)
		do
			create Result.make (start_bound, other.end_bound)
		ensure
			result_exist: Result /= Void
			result_same_as_union: Result.is_equal (union (other))
		end

	intersection (other: like Current): detachable like Current
			-- Intersection with other.
		require
			other_exists: other /= Void
		local
			s: G
			e: G
		do
			s := start_bound.max (other.start_bound)
			e := end_bound.min (other.end_bound)
			if s <= e then
				create Result.make (s, e)
			end
		ensure
			intersects_validity: intersects (other) = attached Result
			result_is_included_by_current: attached Result implies includes (Result)
			result_is_included_by_other: attached Result implies other.includes (Result)
		end

	union (other: like Current): like Current
			-- Union with other.
		require
			other_exists: other /= Void
			intersects: intersects (other)
		do
			create Result.make (start_bound.min (other.start_bound), end_bound.max (other.end_bound))
		ensure
			result_exists: Result /= Void
			result_includes_current: Result.includes (Current)
			result_includes_other: Result.includes (other)
		end
	
feature -- Output

	Io: STD_FILES
			-- Handle to standard file setup
			-- (from ANY)
		once
			create Result
			Result.set_output_default
		ensure -- from ANY
			instance_free: class
			io_not_void: Result /= Void
		end

	out: STRING_8
			-- Printable representation of the current interval.
		do
			Result := "["
			Result.append (start_bound.out)
			Result.append (" - ")
			Result.append (end_bound.out)
			Result.extend (']')
		ensure -- from ANY
			out_not_void: Result /= Void
		end

	print (o: detachable ANY)
			-- Write terse external representation of o
			-- on standard output.
			-- (from ANY)
		do
			if o /= Void then
				Io.put_string (o.out)
			end
		ensure -- from ANY
			instance_free: class
		end

	frozen tagged_out: STRING_8
			-- New string containing terse printable representation
			-- of current object
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			tagged_out_not_void: Result /= Void
		end
	
feature -- Platform

	Operating_environment: OPERATING_ENVIRONMENT
			-- Objects available from the operating system
			-- (from ANY)
		once
			create Result
		ensure -- from ANY
			instance_free: class
			operating_environment_not_void: Result /= Void
		end
	
feature {NONE} -- Retrieval

	frozen internal_correct_mismatch
			-- Called from runtime to perform a proper dynamic dispatch on correct_mismatch
			-- from MISMATCH_CORRECTOR.
			-- (from ANY)
		local
			l_msg: STRING_8
			l_exc: EXCEPTIONS
		do
			if attached {MISMATCH_CORRECTOR} Current as l_corrector then
				l_corrector.correct_mismatch
			else
				create l_msg.make_from_string ("Mismatch: ")
				create l_exc
				l_msg.append (generating_type.name)
				l_exc.raise_retrieval_exception (l_msg)
			end
		end
	
invariant
	start_bound_exists: start_bound /= Void
	end_bound_exists: end_bound /= Void
	start_bound_before_end_bound: start_bound <= end_bound
	current_intersection: intersection (Current) ~ Current
	current_union: union (Current).is_equal (Current)
	has_bounds: has (start_bound) and has (end_bound)
	between_bound: after (start_bound) and before (end_bound)

		-- from ANY
	reflexive_equality: standard_is_equal (Current)
	reflexive_conformance: conforms_to (Current)

note
	copyright: "Copyright (c) 1984-2018, Eiffel Software and others"
	license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)"
	source: "[
		Eiffel Software
		5949 Hollister Ave., Goleta, CA 93117 USA
		Telephone 805-685-1006, Fax 805-685-6869
		Website http://www.eiffel.com
		Customer support http://support.eiffel.com
	]"

end -- class INTERVAL

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